People are using a car to move a long distance. With the help of technological advancement, such a function as a safety function, a convenient function, and the like as well as a transportation function have been included in a car. For example, an air conditioner, a camera and various sensors have been installed in a car. The camera mounted on the car captures a surrounding object of the car and a captured image can be seen to a driver through an internal display of the car. The various sensors installed in the car sense a surrounding object of the car and a sensed signal can be outputted to the driver through an internal output device of the car. A safety device of the car senses an external signal and may be able to give caution to the driver.
Meanwhile, a person passing by a car may not recognize a start of the car or a driver getting out of the car. If the person passing by the car fails to recognize danger, it is highly probable for the person to meet with an accident. Hence, it is necessary to have a technology capable of giving caution to a person who is passing by a car.